Hi there,
I have a cub too. I have found it's cold in summer and hot in winter but no different to being under canvas in any other tent or camper.
I admit to using a heater if I have power, which isn't often, otherwise I get under another cover if I can (eg the big farm shed on a the property we go to). Other than that, another layer and another bevvie!
See you out there!
J